Tests were conducted to confirm the validity of the absolute calibrations which have been performed with the Apollo 17 ultraviolet spectrometer (UVS) in the calibration test equipment (CTE) which were constructed for that purpose. To accomplish this the prototype UV spectrometer SN/01 was retrofitted to be substantially identical to the qualification unit and to the two flight units. It was renamed the cross calibration unit (CCU). The instrument was first calibrated in the JHU calibration test equipment (CTE), then installed in the vacuum optical bench (VOB) at Goddard Space Flight Center and calibrated. The following day a second CTE calibration was conducted which provided substantially the same calibration values as were obtained on the first CTE calibration, and showed remarkably close agreement with the VOB calibration values at two of the wavelengths which were studied. The VOB results at the third wavelength (1216 A) indicate the CTE calibration at 1216 A is 15% too low. This apparent discrepancy is discussed and presents a very important result of the cross calibration effort.